There are many instances in which it is desirable to be able to take a core sample of a timber structure. Forestry workers use such wood cores to evaluate the properties of selected trees--particularly for an analysis of the fibre structure of the tree wood. Electrical power companies and telephone companies use wood cores to test the soundness of the poles on which power and telephone cable are mounted. Structural engineers use core samples of wooden beams, poles and the like to assess the soundness of wooden structures.
A number of devices have previously been used to obtain wood cores. Probably the most popular corer for green wood sampling is a hand-operated tree corer (from Scandinavia) which consists of a hollow steel tube with a tapered spiral external thread on the head. The rotating action cuts the wood fibres on scribes and the cut core slips inside the tube during extraction. The device is operated by quite extreme physical exertion in applying force to a pair of transverse arms extending outwardly from the rear of the T-shaped device. As the corer moves into the tree it compresses the wood tissue around the shaft, rather than removing it, making rotation more difficult the further the corer moves into the tree, particularly when coring wood such as eucalypt which does not compress readily. Risk of muscular injury is therefore quite high. Although this device has the advantages of simple construction and an ability to provide wood cores on soft conifers, it is physically exhausting to use constantly, and extremely difficult to use on hardwood species such as eucalypts.
Another wood corer that has been used in Australia comprises a trepanning head at the end of a long hollow shaft attached to a power drill. This equipment requires a heavy frame, which is clamped to the tree, beam or pole that is being sampled before drilling can commence. In addition to being difficult to transport, it cuts a core with a 25 mm diameter and leaves a hole which has a diameter of 40 mm--which is generally unacceptable from a tree husbandry viewpoint.
There has long been a need for a wood corer which is easy to use and easily transportable, and which cuts a suitable size core quickly, through all species of wood, both green and dry.